CODEWITHSUNDEEP
linuxperl
squareatom
squareatom

Reputation: 96

Runnig OS functions with modified scheduling priority in Perl

Is it possible to have Perl run a Linux OS function with a modified scheduling and/or IO scheduling priority without external commands? I am trying to simulate the following:

nice -n19 ionice -c2 -n7 cp largefile largefile2

Can I somehow do this with File::Copy, the setpriority function, and the CPAN module Linux::IO_Prio? Would I just need to lower the scheduling priority of $0?

EDIT: If I do the following will the priority and IO be lowered for copy()? Is there a better way to do this?

use Linux::IO_Prio qw(:all);
use File::Copy;

setpriority(0, 0, -20);
ionice(IOPRIO_WHO_PROCESS, $$, IOPRIO_CLASS_IDLE, 7);

copy("file1","file2") or die "Copy failed: $!";

Upvotes: 4

Views: 476

Answers (2)

daxim
daxim

Reputation: 39158

Refining Oesor’s answer:

use BSD::Resource qw(PRIO_PROCESS setpriority);
use Linux::IO_Prio qw(IOPRIO_WHO_PROCESS IOPRIO_PRIO_VALUE IOPRIO_CLASS_BE ioprio_set);
BEGIN { require autodie::hints; autodie::hints->set_hints_for(\&ioprio_set, { fail => sub { $_[0] == -1 } } ) };
use autodie qw(:all setpriority ioprio_set);

setpriority(
    PRIO_PROCESS,       # 1
    $$,
    19
);
ioprio_set(
    IOPRIO_WHO_PROCESS,                         # 1
    $$,
    IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, 7)       # 0x4007
);

By the way, you can find out library call and similar stuff with strace.

Upvotes: 1

Oesor
Oesor

Reputation: 6642

You're probably best off simply changing the priority of the currently running pid as needed. Not portable, of course, but doing this is in and of itself non-portable. Anything performing this sort of thing is going to boil down to making the same library calls the external commands do.

my $pid = $$;
`ionice -c2 -p$pid`;
`renice +19 $pid`;

Upvotes: 1

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